Controlled Growth of Unusual Nanocarbon Allotropes by Molten Electrolysis of CO2

Abstract

This study describes a world of new carbon “fullerene” allotropes that may be synthesized by molten carbonate electrolysis using greenhouse CO2 as the reactant. Beyond the world of conventional diamond, graphite and buckyballs, a vast array of unique nanocarbon structures exist. Until recently, CO2 was thought to be unreactive. Here, we show that CO2 can be transformed into distinct nano-bamboo, nano-pearl, nano-dragon, solid and hollow nano-onion, nano-tree, nano-rod, nano-belt and nano-flower morphologies of carbon. The capability to produce these allotropes at high purity by a straightforward electrolysis, analogous to aluminum production splitting of aluminum oxide, but instead nanocarbon production by splitting CO2, opens an array of inexpensive unique materials with exciting new high strength, electrical and thermal conductivity, flexibility, charge storage, lubricant and robustness properties. Commercial production technology of nanocarbons had been chemical vapor deposition, which is ten-fold more expensive, generally requires metallo-organics reactants and has a highly carbon-positive rather than carbon-negative footprint. Different nanocarbon structures were prepared electrochemically by variation of anode and cathode composition and architecture, electrolyte composition, pre-electrolysis processing and current ramping and current density. Individual allotrope structures and initial growth mechanisms are explored by SEM, TEM, HAADF EDX, XRD and Raman spectroscopy.

Controlled Transition Metal Nucleated Growth of Carbon Nanotubes by Molten Electrolysis of CO2

“…The latter part of this study reveals molten electrochemical conditions that produce macroscopic assemblies of CNTs. This study also serves as a sister study [51] in which small electrolytic changes in the 770 °C molten Li2CO3 yield major changes to the product consisting of new, non-CNT nanocarbon allotropes. The rise of this greenhouse gas is causing extensive climate change and damage to the planet's ecosphere, and its mitigation is one of the most pressing challenges of our time [1][2][3][4][5].…”

“…By means of variation of the electrolysis setup, the process could produce, in addition to conventional morphology CNT: doped CNTs, helical CNTs, and magnetic CNTs, as illustrated in Figure 1 [31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Studied applications of electrolytic CNTs from CO 2 include batteries [34], CO 2 transformation from power station flue gas [45], and the substantial decrease in the carbon footprint of structural materials as CNT composites, including CNT-cement, CNT-steel, and CNT-aluminum [8,46], as well as modification of the CO 2 splitting process to yield other CNMs including carbon nano-onions, carbon platelets, and graphene [47][48][49][50][51].…”

“…Catalysts 2022, 12, x FOR PEER REVIEW 3 of 22 transformation from power station flue gas [45], and the substantial decrease in the carbon footprint of structural materials as CNT composites, including CNT-cement, CNT-steel, and CNT-aluminum [8,46], as well as modification of the CO2 splitting process to yield other CNMs including carbon nano-onions, carbon platelets, and graphene [47][48][49][50][51]. The rise of this greenhouse gas is causing extensive climate change and damage to the planet's ecosphere, and its mitigation is one of the most pressing challenges of our time [1][2][3][4][5].…”

Carbon Graphitization: Towards Greener Alternatives to Develop Nanomaterials for Targeted Drug Delivery

“…An approach that is attracting great attention is the electrolysis of CO 2 in molten salt, introduced by The Licht C2CNT (carbon dioxide to CNT) group [ 151 ]. Various CNMs were recently obtained with this method, including CNOs, CNTs, graphene, carbon nanofibers, and other more exotic structures termed carbon nanodragons or nanoflowers [ 77 , 78 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 141 ]. Briefly, experiments were carried out in an alumina crucible containing an electrolyte (typically lithium carbonate), which was heated up to melting.…”

“…A transition metal-based nucleation agent could be added to the cathode or in the molten salt as a catalyst or could originate from the erosion of the anode during the process. This technique is almost costless (excluding the electrodes), and it is very versatile as a large variety of CNMs can be obtained under varying reaction parameters, such as electrode composition, nucleation agent, electrolysis time, and current density [ 78 ]. For example, the presence of metal nucleation agents (typically iron, nickel, or chromium) usually leads to the formation of CNTs, while in their absence, CNOs [ 77 ] or graphene [ 141 ] are produced.…”